Process for improving the pill resistance of two-component acrylonitrile polymers



Aug. 9, 1966 F. J. KO RIK fi fifi PROCESS FOR IMPROVING T PILLRESISTANCE OF TWO-COMPONENT ACRYLONITRILE POLYMERS Filed Sept. 8. 1960 2Sheets-Sheet L F I G" 1 '2 \2 8 g X I IO M '2 T s 4 7 l4 5 3 3 INVENTORFRANK JOSEPH KOVARIK ATTORNEY MERS 2 Sheets-Sheet 2 Aug. 9, 1966 F. J.KOVARIK PROCESS IMPROVING THE PILL RESISTANCE TWO- NT ACRYLONITRILE POLYPONE Filed Sept. 8, 1960 FIG-1A INVENTOR FRANK JOSEPH KOVARIK ATTORNEYUnited States Patent 3 264 705 PROCESS FOR IMPRovrN THE PILL RESISTANCE0F TWO-CONWONENT ACRYLONITRILE PQLY- MERS FrankJoseph Kovarik,Waynesboro, Va., assignor to E. I. du Pont de Nernours and Company,Wilmington, Dei.,

a corporation of Delaware Filed Sept. 8, 1960, Ser. No. 54,697 5 Claims.(Cl. 28-76) This invent-ion relates to improved crimped compositefilaments and a process of making them.

It has been proposed to produce helically crimped composite syntheticpolymeric filaments having the capacity of changing the amount of crimpupon being exposed to the effect of a swelling agent and upon revertingto the original crimp upon removal of the swelling agent. Thischaracteristic is, for convenience, referred to as reversible crimp andis observed by the squirming of the filaments upon both application andremoving of the swelling agent. The value of this crimp reversibility isevidenced by the ability of the filaments in yarns, when embodied in afabric, to squirm or twist around in the fabric under the influence of aswelling agent such as water (and also on removal of the swellingagent), but, nevertheless, to regain the original crimp in the fabricwith removal of the swelling agent, as by drying. 'Fabrics containingthese filaments acquire a high degree of fullness or covering power as aresult of the swelling treatment and retain or even increase thisfullness after being subjected to such treatments repeatedly.

It has been found that the high degree of crimp reversibility in thefibers necessary to produce yarns and fabrics with good bulk,compressional resilience, response to finishing treatments, and recoveryfrom glazing is generally accompanied by a high level of crimpfrequency. This high level of crimp frequency leads to a rough wool-likehandle in knitawear and woven-wear fabrics and does not afford softfabrics similar to those made from cashmere, for example.

For some applications, especially in fabrics from woolen-spun yarns, theuse of these recent fibers is restricted by a phenomenon known aspilling.

One object of this invention is to produce a crimped composite filamentsthat aifords fabrics that are density stable to washing and ironing andare pill resistant.

Another object is to produce composite filaments having a reversiblecrimp and a low level of crimp that affords soft, cashmere-like fabrics.

These and other subjects are accomplished as described more fully below.

Filaments of the invention consist of at least two fiberformingcompositions of polymers of acrylonitrile in eccentric relationship atleast one of which contains 50 or more milliequivalents per kilogram ofpolymer of ionizable groups in excess of the ionizable groups containedin the other components. After the filaments are extruded and the fiberstructure established, the solidified fibers are drawn from 1.1 to X andrelaxed in the presence of a plasticizing medium such as steam under atension of at least 0.01 gram per denier. The extent of relaxationshould be at least 50% of the boil-off shrinkage of the as-drawn yarnprior to drying the filaments. After relaxation, the fibers aremechanically crimped if desired, then dried and given a hot relaxationtreatment to permit the development of a helical crimp.

More specifically, the composite filament comprises at least 2 polymersof acrylonitrile eccentnically disposed toward each other and has 5 to10 helical crimps per inch of extended length, a crimp product of lessthan 100, a crimp reversibility (ECR) of -50%, a tenacity of at least 2grams per denier and is characterized by a high ice resistance topilling when spun into yarn and knitted or woven into a fabric.

The amount of relaxation may vary from 50 to 99-]-% of the boil-oifshrinkage of the as-drawn yarn. Preferably a relaxation of at least ofthe boil-off shrinkage of the as-drawn yarn is used. Boil-off shrinkageis that fiber shrinkage which takes place upon exposure to boiling waterfor a period of at least about 5 minutes.

The length of time of the relaxation treatment is not critical and maybe from 0.5 second to 10 minutes. Preferably, this is from 0.5 to 2seconds when it is used as part of a continuous process.

The relaxation can take place in any type of heating medium having atemperature of about 100 C. which has a plastioizing action on the yarnsuch as organic vapors, or steam. Steam at pressures of from 0 to 5p.s.i. gage is preferably used. Temperatures as high as 120 C. may beused.

The process can be continuous or batch. Preferably the relaxation isdone continuously in conjunction with a wash-drawing process as thisaffords lower crimp levels. The beneficial results of pill reduction offabrics containing the fibers may also be obtained by a batch processwherein the drawn and wet filaments are lagged in some manner as in cansbefore the relaxation step.

The process is most advantageously used on tows of 5,000 to 450,000denier.

By the expression polymer of acrylonitrile is meant the homopolymer ofacrylonitrile or copolymers of acrylonitrile and monoethylenicallyunsaturated addition type monomers containing at least acrylonitrile.Suitable comonomers include the ethylenically unsaturated sulfonic acidsas methallyl sulfonic acids and others as disclosed in US. Patents2,527,300 and 2,601,256 and other monomers as disclosed in Jacobson US.2,436,- 926 and in Arnold US. 2,456,360.

The two polymers selected as components must have the requireddifference in shrinkage and in swellability so that the compositefilament crimps and a reversible crimp results. To develop crimp in thecomposite filaments, the shrinkability of one component should be atleast 0.2% greater than the shrinkability of the other component, thatis, said component has at least 0.2% greater loss of the original lengthupon shrinkage than the other component. The shrinkability of acomponent is determined by measuring the shrinkage, upon immersion inboiling water under no tension, of a monocomponent filament made fromthe component polymer (spun and otherwise processed under substantiallythe same conditions as the composite filament). One component of thecrimped filament should have a reversible length change after shrinkageof at least 0.05% and preferably at least 0.10% more than that of theother component, that is, said component has at least 0.05 greaterchange in length of the original length upon swelling than the othercomponent. The reversible length change of a component is determined bymeasuring the increase in length of a monocomponent filament of thecomponent polymer (spun and subjected to after-treatments under the sameconditions as the composite filament) upon being immersed in the aqueousmedium used for the testing of the crimp reversibility of the compositefilament. Measurements are obtained with strands of approximately denierand approximately 15 inches long as follows: The samples (previouslyrelaxed by a boil-off) are clamped in a tensile tester with a smallamount of slack and held in the proper medium (air, cold water, or hotwater) for about 2 minutes. The mechanically driven clamp is thenstarted at a low rate of elongation (0.3 inch per minute); it is stoppedand reversed immediately when the stressstrain curve starts to departfrom the zero line. The true length of the sample is then calculatedfrom the clamp distance in the starting position and the chart distancebe tween the start of the test and the point where thestressstrain'curve began.

After wet tests the samples are dried (while clamped) by means of a hairdryer, and the length of dry strand at room temperature determined asabove. Wet to dry cycles are repeated until the length change becomesconstant. As a rule some shrinkage occurs during the first cycle. Formost samples, satisfactory results are obtained with three cycles.

The reversible length change is calculated in percent, based on thefinal dry length of the sample.

length wet-length dry 100 Reversible length change: final length yResults from at least four different strands are averaged.

to obtain a representative value. Suitable polymers, methods forselecting them, and crimping methods such as by heat, :boil-oif orsteam'are described in coassignedand copending Taylor application,Serial No. 771,677, filed November- 3, 1958, now US. Patent 3,038,237.

The crimp reversibility of the composite filaments of' this invention isdetermined by the following test.

A single filament is separated from. the single end or tow of drawn,unrelaxed fibers. A three-inch length of the filament is attachedto-opposite sides of a rectangular copper Wire frame with 30% slack.between the ends. .The

rack and filament is then boiled off for minutes to develop the crimp.The 'crimped filament is then transferred to a special viewing holderbytapingor gluingthe ends so that about 10% slack is present and thefilament length between the clamped ends is approximately 2.5 inches.The filament and viewing holder are then mountedvertically in astoppered test tube containing desiccant. The tube is stored verticallyovernight: (1824 hours) at 70 C. Following this conditioning period todry the filament the tube is then brought to room temperature(approximately 25 C.). After allowing 30 minutes for cooling, the totalnumber of crimps in thefilament between the fixed ends is counted. Incounting, any crimp reversal points present are ignored. The desiccantis then removed from the glass tube, the tube filled with water andstored vertically at 70 C. for 6 hours. The number of crimps in the. wetfiber is counted as above.

The cycles are repeated as required to obtain reproducible results. Theequilibrium crimp reversibility (ECR) or relative change in crimps/inchof extended length from 25 C. dry to 70 C. wet is obtained by thefollowing yarn as measured under suflicient tension topull out the crimpand give an essentially straight filament or yarn. All crimp counts arestated in terms of extended length.

The crimpindex of a fiber is determined on a sample that has been boiledin water and then dried in room temperature air. 150 milligrams isdetermined (L This force is suificient to straighten the fiber fromcrimps. The load on the fiber. is then reduced to 5 milligrams and thecrimped length (L determined. Crimp Index (C.I.) is calculated asfollows:

Crimplndex X 100 The length of the fiber under a load of The crimpfrequency is similarly determined on fibers that have been boiledinwater and dried in room temperature air. The product of crimpindexandcrimp frequency is known as crimp product.

The necessary differential reversible length change. be-.

tween the components is readily obtainedby altering the content ofionizable groups in the two polymers.

Such ionizable. groups are readily obtained by-co polymerizingacrylonitrile, for! example, 'With monomers containing acid.groupssuch'as carboxylic, sulfonic or phosphonic in either the saltcrime-acid form.

The following sulfonated polymerizable monomers and 1 their salts areeminently suited for use in thisinvention: p-styrenesulfonic acid,methallylsulfonic acid, allylsulfonic acid and ethylenesulfonic acid.

It will be obvious to those skilled in theart that the re,- quiredionizable groupscanbeincorporated into a polymeric component :by theblending of 2 or more poly-.

mers. The polymers should preferably be compatible.

The inclusion of from /2-15.% of certain non-ionic modifiers incopolymers of acrylonitrile'; enhancesthe ef-' fect of any ionizablegroups present in the final polymer.

In general, it has been found that'the monomers that are effective in:this connection are also the sameamonomers which, when incorporatedintoan acrylonitrile polymer increases the ;dyeabilityof'fibersmade'the'refrorn with a disperse dye, such as the blue-dispersedye'Prototype 62.]

Among the more desirable-monomers from the point ofview of enhancing theeffect of ionizable group content are methyl jacryla'te,-methylmethacrylate, .methyl vinyl ketone,.- acrylarnide,N-tertiarybutylacrylamide, vi-

nyl methoxyethylether, methoxyethylacrylate' and vinyl 1 acetate;

Pilling is a well-known:phenomenon of :fabrics madel 7 from staple fiberyarns, and can be described as the tendency to form smallfclusters,clumps, .or balls or inter-.

entangled fiber endson the surface of a fabric; Pilling propensity canbe measuredby actualwear tests or by laboratory tests. The testdescribed inthe article, Random Tumble Filling Tester, by M. Baird etal. in Textile Research Journa1'26, 731-735 (1956) isused herein.-

The pilling ratings are expressed as numbers from,3

(verysevere pilling'), to +5 .(110 pilling All times, are

for 20 minutes, exposure unless otherwise stated. 7

Loop work-to-break. This is the areaunder the stressstrain curve of aloop of filament as-determined on an 1 The units are ingram-cm./denier-cm. This property and theelongation of a loop at break(loop Instron tester.

elongation) are considered to be indicative of the toughness of thefiber.

The expression intrinsic viscosity With',the symbol i (n) as used hereinsignifies the value of ln(n) at the ordinate axis intercept (i.e., when0 equals 0) in agraph of' as ordinate with 0 values (grams per ml. ofsolution) asabscissas. (n) is a symbol for relative viscosity, which isthe ratio of the flow times in a viscosimeter of a poly-.

ln is the logarithm to the mer solution andthe solvent.

base. 2. All:measurements onpolymers containing acrylonitrile combinedin the, polymer .moleculef. were made with DMF solutions at 25 5 CaReferring to the. drawings:

FIGURE 1 is a central cross-sectional elevation of a spinneret assembly.which can. be, used to make .the composite filamentspof this invention;

FIGURE 1A is an enlarged portion taken from FIG URE. l to show detailsofthe spinneret. at the spinning orifice;

FIGURE 2 is a transverse. crossesectional plan view of the apparatus ofFIGURE '1 taken at 2+2 thereof and showingdetails of the top ofthe backplate;

FIGURE 3 is a transverse cross-sectional plan view" taken at 3-3 ofFIGURE 1 showing details of the bottom of the back plate;

FIGURES 4, 5, and 6 show greatly magnified cross sections, i.e.,sections perpendicular to the filament axis, of typical filaments ofthis invention produced by dry spinning. In these drawings one componentis shaded to show the separation between components; and

FIGURE 7 is a schematic representation of apparatus that can be used inpracticing the present process.

With reference to FIGURE 1, the bottom spinneret plate 2 which containsa circle of orifices 3 is held in place against back plate 1 byretaining rings 12 and 14 and by bolt 13. A fine-mesh screen 4 e.g., 200mesh per inch, is pressed into position between, and serves as a spacerbetween, spinneret plate 2 and back plate 1. Back plate 1 contains twoannular chambers 8 and 9 which are connected to suitable piping andfiltration apparatus (not shown) to receive different spinningcompositions. Lead holes 11 go from annular chamber 9 to annular space'7. Lead holes lead from annular chamber 8 to annular space 6. Annularspaces 6 and 7 are separated by wall 5 which is disposed above orifices3 and spaced from spinneret plate 2 by screen 4 to permit free andcontiguous passage of the spinning fluids from annular spaces 6 and 7through orifices 3, the mesh of screen 4 being fine enough to permitspinning fluid passage through orifices 3, as shown in detail in FIGURE1A.

In FIGURE 2 are shown four lead holes 10 and four lead holes 11 equallyspaced within the concentric chambers 8 and 9, respectively.

In FIGURE 3 are shown the concentric inner and outer annular spaces 6and 7, sections of bottom spinneret plate 2 and the fine-mesh screen 4partially in section.

Operation of the described apparatus in the practice of this inventionis readily understood. Separate spinning materials are supplied to theinner annular chamber 9 and outer annular chamber 8, respectively, ofthe back plate; the former flows from chamber 9 through the lead holes11 into the inner annular space 7 and thence through screen 4 andorifice 3 to form a part of a composite filament, while the latterpasses through the lead holes 10 to the outer annular space 6 and thencethrough screen 4 and the outer side of the orifice 3 to form the otherpart of the composite filament.

FIGURE 7 is a schematic view of a wash-draw machine followed by adiagrammatic representation of a fluid relaxation chamber and a crimper.Tow is drawn over rollers 25, 26 and through a series of water baths,21, 22, 23, 24 while maintained under tension. This wash-draw treatmentserves to extract solvent while the yarn is being drawn. The drawn yarnis then forwarded to a steam chest 28 for controlled relaxation and maythen be passed directly to a crimper 30.

Example 1 A 20% solution in dimethylformamide (DMF) of polyacrylonitrileof (n) 2.0 and containing 27 milliequivalents of acid groups perkilogram of polymer (as determined by titration in a DMF solution) isextruded into a spinning cell as one component (which faces the centerof the spinning cell) of a composite filament using a spinneret as shownin FIGURE 1. Simultaneously, a 27% solution in DMF of a copolymer ofacrylonitrile/ styrenesulfonic acid, 96/4% by weight composition, of (n)1.5 and analyzing 240 milliequiva-lents of acid per kilogram of polymeris extruded as the other component (which faces the Wall of the cell) ofcomposite filaments. The spinneret contains 140 orifices 0.007 inch indiameter located on a 5.27 inch diameter circle. A mixture of carbondioxide and nitrogen gases at 320 C. is circulated through the spinningcell, the wall of which is maintained at 180 C. The solutions areextruded at 105 C. The threadline (1090 total denier) consisting of 140composite filaments is Wound up at 200 yards per minute (y.p.m.).

Three-hundred-thirty ends of yarn produced as above with a combineddenier of 360,000 are combined into a tow and drawn to 4 times itsoriginal length (i.e., 4 X draw ratio) through a series of water bathsat 98 C. which extract the residual DMF. Th'e drawn and extracted tow isled directly from the wash-draw process to a stufier box crimper similarto that shown in Hitt U.S. 2,747,233 where it is crimped to an extent of67 herring bone crimps per extended inch using a stuifer box temperatureof 50 C. The crimped tow is then cut into 3% length staple. The cutstaple, loosely arranged in a tray, is dried for 15 minutes in acirculating air oven at 270275 F. The dried staple (designated as ItemA) has a weak mechanical crimp of 6-7 crimps per inch plus 68 helicalcrimps per inch of extended length.

The above process is repeated'using the same components, spinningconditions and wash-draw conditions but with the significant change ofplacing an 8 foot long steam cell between the end of the wash-drawapparatus and the stulfer box crimper. The drawn and washed tow ispassed into the steam cell containing steam at atmospheric pressure at aspeed of y.p.m. and is forwarded from the other end of the steam cell at128 y.p.m. where it is fed continuously to the stuffer box crimper. Th'etow is relaxed to an extent of 20% in the steam cell during the 1.0second time of exposure to the steam. The crimped tow is then cut anddried as above, to yield a product of this invention designated as ItemB. The as-drawn yarn has a boil-off shringage of 21%.

Both Items A and B are fibers of good quality and have the followingcommon properties after boiling in water: a density (as determined in aheptane-carbon tetrachloride gradient tube) of 1.189, an ECR value ofabout 40%, a tenacity of 2.2 grams per denier, a straight elongation atthe break of 30%, and an initial modulus of 50 grams per denier. Otherproperties in which the two items vary significantly are shown in TableI.

Knitted fabrics are made from various spunyarns of the two items and thepilling resistance tested. The superior pilling properties of fabricsmade from yarns of this invention (Item B) are surprising.

A third staple fiber is made as Item B using the steam cell but omittingthe stuffer box crimper. Samples taken from the tow before the cutterare straight and uncrimped. These fibers that have not been mechanicallycrimped have essentially the same properties as Item B above.

Sweaters and woven fabrics made from the yarns of this invention (ItemB) have a soft cashmere-like handle particularly when treated with afiber lubricant. Fabrics of similar construction made from Item A haveharsh handles similar to that of number 70s wool.

TABLE I Item A Item B Steam relaxed No Yes Helical crimps/inc 13 Crimpindex 10 5 Residual shrinkage, percent 3 1 Loop elongation, percent 1017 Loop, Work to break 0. 14 0 21 Filling ratings on knitted fabricsfrom:

Worsted ply yarn (20/2 cotton count 14 Z/7 S tw1st) --2. 2 +3. 5 Cottonsingles (10 cotton count 8.5 Z) 3. 0 +2. 5 Woolen singles (5.1 wool run,14 Z) -2. 5 +0. 5

The rating of -3.0 indicates very severe pilling as compared with +5 forno pilling.

Results similar to those of Item B are obtained when the wet drawn towis fed into cans and lagged for 24 hours before passing through thesteam cell. When using this batch method it is important that the storedtow be fed to the steam cell in an open form equivalent to that obtainedfrom the draw machine.

A portion of the crimped tow of Item B is cut to 3-inch lengths andanother portion is cut with lengths.

continuously varying from A to 3 /2 inch on a modified Beria staplecutter and dried. Worsted ply yarns (2/30 worsted count with an .8 Z/3.5S turns perin'ch yarn twist) are spun from both lots of cut staple andknit tubing of similar construction prepared on a 12 cut I acquardknitting machine. The fabric from 3-inch (square cut) staple has apilling rating of 2.3 as contrastedvwith 4.5

for the fabric from theyariable length staple. The ad: vantages .ofusing the variable length staple are'even more striking with fullfashion knit fabrics.

by continuouslydrawing, passing through. an 8 footcell.ccxnt-ainingatmospheric steam, cutting to. staple length and drying at-130 C. The speedof the output rolls is varied to control the amount ofrelaxation :in the steam cell..

Similar cotton singles type yarns are spun from all items, fabrics ofsimilar construction knitted and: submitted to the pilling test for.20.minutes.= The pilling ratings are given in Table 'II.I The crimpyperinch. and density of the dry samples after boiling in water are given ,1

in TableII.

TABLE II Steaming Residual Item Steaming Conditions Relaxation,Shrinkage Density Filling Crimps/inch percent After Steaming On piddledtow 0-1 1.160 +1 14 On wet staple 20 0-1 1. 159 +1 14 On dry staple 30-1 1. 185 2. 0 On Wet tow-tensi0ned 0 21 1. 189 -3. 0 12 do 18 13 1.189+3.5 7 do 20 13 1. 190 +3. 5 7

Example 11 Composite filaments having as onecomponent. an

88/ 12%.mixture (analyzing SSmi-lliequivalents of acid per kilogram ofpolymer) of polyacrylonitrile-of. (n)

2.0 and the copolymer acrylonitrile/sodium styrene sulfilaments as inExample I. The 4 x drawn, cut and dried (3009.1 staple is'designated asItem C.. Therasedrawn yarn has a boil-off shrinkage of 21%.

Item D is made as above except for the inclusion of the steam, cell ofExample I to provide 19% relaxation of the 40,000 denier tow between thewash-drawmachine and thestufler box crimper.

Both items of this example have high crimp reversibility (ECR of 40%)and a density of 1.185 after boiling in water. I

The .staple of Item C develops over 18 helical crimp per inch ofextended length when boiled free of restraint in Water. It has a crimpindex of 18. Item:D develops only-6 helical crimps per inch afterboiling in water.. It has a crimp index of 7.

Worsted ply yarns (20/2 cotton count, 11 'Z/'5.5 twist) are spun fromboth items and knit fabrics of similar construction made. The fabricfrom Item C has a harsh raspy handle as contrasted with the softandcashmere-like handle of the fabric from Item D. The latter fabric hasan improved pilling rating over the fabric of Item C of 2 rating units.

Example III piddled from side to side onto a continuous belt and thensubmitted to steam at atmospheric pressure for 2 minutes,-

which causes the tensionless tow to shrink about 20% Those fibers havingdensities less than about =1.170are They have a tendency to absorb ianvery undesirable. unusual amountof finish whichmay lead to odordiflicultiesin afinal yarn. Theytake up ;a great deal ofdye from a dyebathlbut yet'yielda relatively low color in the yarn. Furthermore, infabrics they display an instability in density which causes theappearance of dyer streaks and lusterstreaks depending uponthe pressureplaced on the fabric in ironing procedures. To the contrary the fibers.having a density of 1.180 to 1.200 are density stableand are notaffected by these deficiencies:

Itiis surprising that the steaming process of this inven-' tion :persedoes not completelyfredu ce the yarn shrinkage inthis process. As thefigures; indicate, there iszappreciable residual shrinkage before dryingin such filaments and it:is the high temperature drying step :that setsthe yarn and reduces shrinkage.

Example IV The spinning conditions of Example I are repeated to producecomposite. filaments having cross sections similar,

to those shown in FIGURE6. 20 ends of the as-spun yarn are pliedto givean .8000 denier: tow which is then drawn a total.of 2 using theapparatusof. Example I. The as-drawn yarn has a boil-01f shrinkage of about 45%.

The tow is then .cut and dried on trays in an oven at 130 C. to formItem M. L

Item N is formed using the same conditions as for M but with theinclusion of the steam cell of Example I and with the adjustment of theoutput rolls so that the toW has=0% relaxationd-uring thesteamtreatment.

Item 0: is made in thesame way as N with the exception that the towis'allowed to relax a total of 37% during the steaming operation; e

The abovethree processes are repeated with the substitution of a 20%solution-of polyacrylonitrilewof (n) 2.0

and spontaneously crimp. The crimped tow is out to a staple length anddried with 130 C. air for 10 minutes to provide Item E. 7

Item F is prepared by passing the above drawn bust uncrimped tow to astaple cutter and then depositing the wet and a 21% solution of,thecopolymer of Example I of (n) 2.0 to yield composite filaments:having a cross sec-' tion similar: to FIGURE 5.

tained with no steam cell, 0% relaxation in the steam cell.

Items 1 Q, and R are oband137% relaxation in the steam cefllrespectively.

The above processes yielding Items P, Q, and R are repeatedwith thereversal of the two spinning solutions in the spinning head so that theouter portion'of the composite filament containing thehom-opolymer facesthewall of the spinning celli This produces filaments of cross sectionsimilar to FIGURE 4.; Items*S, T,' and U are obtained with no steam-cel1, 0% relaxation in the steam cell and 37% relaxation in the steamcell'respectively Pilling. ratings are determined from knit fabricsv ofwoolen single type yarns (5.1 run/ 8.52 twist) spun from the samples.

All items have ran ECR of about 2530% and other filament properties asshown in Table III after boiling in water.

TABLE III Residual Loop Elon- Pilling Rating Item Cross Section SteamingConditions Crnnps/meh Shrinkage, Density gation, Work to percent percentBreak MP, and S Fig. 4, 5, or 6 None 12 l. 5 1.189 9-13 0.06 3 3 3 N, Q,and T. Fig. 4, 5, or 6 Tent relax 20 3 1.189 21 .36 3 3 -3 R Fig.-dogbone.- Tensioned 37% relax 0 1.189 64 .82 -1 +3 +5 Fig. 4-dogbone. d0 1. 187 48 -1 0 +3 Fig. 6 ac0rn. 0 1. 190 +3 +5 +5 Example V Thisexample shows the advantages of the process of this invention with 1.35X drawn fibers.

Fibers of the same composition as those in Example I are spun in thesame manner except for spinning speeds of 400 y.p.m. and for thesolution, head and cell temperatures of 60, 270 and 160 C. respectively.Four hundred fifty ends of the as-spun yarn (280 denier) are plied togive a 126,000 denier tow which is then drawn a total of 1.35 using theapparatus of Example 1. The tow is then cut and dried on trays in anoven at 130 C. to form Item V.

Item W is formed using the same conditions as for V but with theinclusion of the steam cell of Example I and allowing the tow to relax atotal of 20% during the steaming operation. The as-drawn fiber has ashrinkage of about 22%.

Both fibers developed a helical crimp of about 9 crimps per inch whenboiled free from restraint in water and have a negative crimpreversibility of ECR. Properties of the boiled-oil fibers and knitfabrics prepared from them are given in Table IV.

TABLE IV Item V Item W Density 1. 184 l. 189 Loop Elongation, percent.6. 2 9. 8 Loop, Work to Break 0. 06 0.09 Filling Ratings on Fabrics fro5.1 run, 8.5 Z twist, 20 minutes 1 +5 Yarns made from Item W aresignificantly tougher than V as indicated by the loop properties. Thisresults in improved knittability of these low tenacity fibers comparedto Item V.

Example VI A 21% solution in dimethylformamide (DMF) of a mixture of 86%of polyacrylonitrile of intrinsic viscosity 2.0, and containing 22milliequivalents of acid groups per kilogram of polymer (as determinedby titration in a DMF solution) and 14% of a copolymer ofacrylonitrile/styrene sulfonic acid, 96/ 4% by weight composition, ofintrinsic. viscosity 1.5, and analyzing 240 milliequivalents of acid perkilogram of polymer, said mixture of polymers containing 53milliequivalents of acid groups per kilogram of polymer used, isextruded as one component (which faces the center of the spinning cell)of a composite filament using a spinneret having three concentric ringsof orifices, totaling 252' in number. This solution also contains 0.04%TiO based on total polymer content. Simultaneously, a 27% solution inDMF of a copolymer of acrylonitrile/styrene sulfonic acid, 96/4% byweight composition, of intrinsic viscosity 1.5, and analyzing 240milliequivalents of polymer and also containing 0.4% TiO polymer contentused, is extruded as the other component (which faces the wall of thecell) of composite filaments.

acid per kilogram of based on total 2,050 total denier, Item B)consisting of 252 composite filaments is wound up at 350 yards perminute.

Five-hundred seventy-six ends (Item A) or 635 ends (Item B) of yarnproduced as above with a combined denier of 1,300,000 are combined intoa tow and drawn to four times its original length (i.e., 4 X draw ratio)through a series of water baths at 98 C. which extract the residual DMF,said water baths containing mixtures of DMF and water with not over 30%DMF.

For Item A, the drawn and extracted tow is led directly from thewash-draw process to a stuifer box crimper similar to that shown inHitt, US. 2,747,233, where it is crimped to an extent of six to sevenherringbone crimps per extended inch using a stuffer box heated by steamat a pressure of 3 p.s.i.g. The crimped tow is then cut into staple oflengths continuously varying from 1 to 5 inches on a modified Beriastaple cutter. The cut staple is dried on a moving belt dryer at C. fortwenty-five minutes. The dried staple (designated as Item A) has a weakmechanical crimp of 5 to 6 crimps per inch plus 5 to 6 helix crimps perinch of extended length.

For Item B, the above process is repeated using the same components,spinning conditions, and Wash-draw conditions, but with the significantchange of placing an eight-foot long steam cell between the end of thewashdraw apparatus and the stuffer box crimper. The drawn and washed towis passed into the steam cell, containing steam at atmospheric pressure,at a speed of 200 yards per minute where it is fed continuously to theunheated stuifer box crimper. The tow is relaxed to an extent of 15% inthe steam cell during the 0.94 second time of exposure to the steam. Thecrimped tow is then cut and dried as above, to yield a product of thisinvention designated as Item B.

Items A and B have the following common properties after boiling inwater: a density (as determined in heptanecarbon tetra-chloride gradienttube) of 1.189, an ECR value of 30%, a tenacity of 2.5 g.p.d., and astraight elongation at break of 32%. Properties in which the two itemsvary significantly are shown in Table V.

What is claimed is:

1. In a process for preparing staple fiber from composite filaments, theresulting staple fiber having improved resistance to pilling whichcomprises simultaneously washing and drawing a tow of continuousfilaments wherein said filaments have two eccentri-cally positionedsections of different acrylonitrilepolymers extending along theirlengths, the improvement which comprises a controlled relaxation stepprovided by continuously passing said filaments under a slight tensionthrough a heated pliasticizing medium, the tension on said filamentsland the tem-perm ture of said'medium being controlled to uniformlyshrink said filaments an amount equal to at least 50% of the.

3. The process of claim 1 wherein said filaments are.

drawn from about 1.1 to 10 times their original length and aftershrinking are crimped.

4. The process of claim 1 wherein said medium issteam.

5. The process-of claim 1 wherein the relaxation treatment under tensionis carried out in the presence of steam at about 0to 5 psi. gage.

References Cited bythe Examiner UNITED STATES PATENTS Sisson etal 28 -82Sisson; -28-82 Appleton et al 28-72 X Rokosz 28-72 Spence et a1. 28-72Pit'zl 28-7 2 Breen et al ,l61-'177 X Taylor 161-172 Wu 161-175 FOREIGNPATENTS Great Britain.

ROBERT'R. MAC-KEY, Primary Examiner. 2 RUSSELL C. MADER, DONALD W.PARKER, 0 2

LB. MAIER, A. J. FSMEDEROVAC,

Examiners. 1

Assistant Examiners.

1. IN A PROCESS FOR PREPARING STAPLE FIBER FROM COMPOSITE FILAMENTS, THERESULTING STAPLE FIBER HAVING IMPROVED RESISTANCE TO PILLING WHICHCOMPRISES SIMULTANEOUSLY WASHING AND DRAWING A TOW OF CONTINUOUSFILAMENTS WHEREIN SAID FILAMENTS HAVE TWO ECCENTRICALLY POSITIONEDSECTIONS OF DIFFERENT ACRYLONITRILE POLYMERS EXTENDING ALONG THEIRLENGTHS, THE IMPROVEMENT WHICH COMPRISES A CONTROLLED RELAXATION STEPPROVIDED BY CONTINUOUSLY PASSING SAID FILAMENTS UNDER A SLIGHT TENSIONTHROUGH A HEATED PLASTICIZING MEDIUM, THE TENSION ON SAID FILAMENTS ANDTHE TEMPERATURE OF SAID MEDIUM BEING CONTROLLED TO UNIFORMLY SHRINK SAIDFILAMENTS AN AMOUNT EQUAL TO AT LEAST 50% OF THE BOIL-OFF SHRINKAGE OFSAID DRAWN FILAMENTS, AND CONVERTING THE RESULTING TOW OF RELAXEDCONTINUOUS FILAMENTS TO STAPLE FIBER AND DRYING THE STAPLE FIBER AT HIGHTEMPERATURE.